// returns true if we performed an UTF-8 decoding
static bool encodedUtf8ToUtf16(QString &result, ushort *&output, const ushort *begin, const ushort *&input,
const ushort *end, ushort decoded)
{
int charsNeeded;
uint min_uc;
uint uc;
if (decoded <= 0xC1) {
// an UTF-8 first character must be at least 0xC0
// however, all 0xC0 and 0xC1 first bytes can only produce overlong sequences
return false;
} else if (decoded < 0xe0) {
charsNeeded = 2;
min_uc = 0x80;
uc = decoded & 0x1f;
} else if (decoded < 0xf0) {
charsNeeded = 3;
min_uc = 0x800;
uc = decoded & 0x0f;
} else if (decoded < 0xf5) {
charsNeeded = 4;
min_uc = 0x10000;
uc = decoded & 0x07;
} else {
// the last Unicode character is U+10FFFF
// it's encoded in UTF-8 as "\xF4\x8F\xBF\xBF"
// therefore, a byte higher than 0xF4 is not the UTF-8 first byte
return false;
}
// are there enough remaining?
if (end - input < 3*charsNeeded)
return false;
if (input[3] != '%')
return false;
// first continuation character
decoded = decodePercentEncoding(input + 3);
if ((decoded & 0xc0) != 0x80)
return false;
uc <<= 6;
uc |= decoded & 0x3f;
if (charsNeeded > 2) {
if (input[6] != '%')
return false;
// second continuation character
decoded = decodePercentEncoding(input + 6);
if ((decoded & 0xc0) != 0x80)
return false;
uc <<= 6;
uc |= decoded & 0x3f;
if (charsNeeded > 3) {
if (input[9] != '%')
return false;
// third continuation character
decoded = decodePercentEncoding(input + 9);
if ((decoded & 0xc0) != 0x80)
return false;
uc <<= 6;
uc |= decoded & 0x3f;
}
}
// we've decoded something; safety-check it
if (uc < min_uc)
return false;
if (isSurrogate(uc) || isNonCharacter(uc) || uc > 0x10ffff/*QChar::LastValidCodePoint*/)
return false;
if (!QChar::requiresSurrogates(uc)) {
// UTF-8 decoded and no surrogates are required
// detach if necessary
ensureDetached(result, output, begin, input, end, -9 * charsNeeded + 1);
*output++ = uc;
} else {
// UTF-8 decoded to something that requires a surrogate pair
ensureDetached(result, output, begin, input, end, -9 * charsNeeded + 2);
*output++ = QChar::highSurrogate(uc);
*output++ = QChar::lowSurrogate(uc);
}
input += charsNeeded * 3 - 1;
return true;
}
// Returns true if the code point is an Unicode character (that is,
// an Unicode scalar value excluding noncharacters).
inline constexpr bool isUnicodeCharacter(code_point_t code_point) {
return isUnicodeScalarValue(code_point) and not isNonCharacter(code_point);
}
